I am often asked the best way to clean zinc nazi coins my advice is always the same NEVER!
By cleaning you remove years of history which can never be recovered okay you might have a nice clean coin but the value of your coin to most collectors will drop by as much as 90% of its uncleaned value.
Dirt and grime may look unsightly but try to imagine whos hands these coins have passed through and if they could speak what stories could they tell this makes it easier to avoid the temptation to clean.
The two coins above are good examples of uncleaned third reich zinc coins although they may look unsightly the history is there to see.
Enjoy your ebaying